1. Field of the Invention
The present invention relates to switching power supply apparatuses each supplying power to a plurality of loads.
2. Description of the Related Art
A switching power supply apparatus which supplies power to a plurality of diode loads needs to have a configuration in which DC voltages are output from a plurality of output units. The switching power supply apparatus disclosed in Japanese Unexamined Patent Application Publication No. 10-28376 employs a configuration in which a plurality of DC voltages are obtained by providing a plurality of secondary windings and performing rectification and smoothing.
In the switching power supply apparatus disclosed in Japanese Unexamined Patent Application Publication No. 10-28376, a switch device and a capacitor are connected to one of two secondary windings and a first DC voltage is output to a first load. A diode and a capacitor are connected to the other of the two secondary windings and a second DC voltage is output to a second load. The first DC voltage which varies in accordance with the power consumption of the first load is detected, and based on the detection result, switching control of the switch device on the primary side of the transformer is performed. As a result, stabilization of the first DC voltage is realized even when the power consumption of a load significantly changes.
In the switching power supply apparatus disclosed in Japanese Unexamined Patent Application Publication No. 10-28376, the switching control of a switch device on the primary side of the transformer is targeted at the first DC voltage. Hence, even when the second load is constant, the second DC voltage varies due to the switching control of the switch device on the primary side of the transformer in accordance with variations in the first load. Further, for example, a surge current may be generated and flow through the second load due to a sudden change in the first load. This surge current may cause noise to be generated on the load side, whereby the characteristics on the load side may be affected or a current exceeding the rated current may flow through the second load.